1. The Field of the Invention
The present invention relates generally to optical transmitters. More specifically, the present invention relates to optical transmit assemblies in which a temperature sensing device is patterned on an electro-optic transducer die.
2. Background and Related Art
Computing and networking technology have transformed our world. As the amount of information communicated over networks has increased, high speed transmission has become ever more critical. Many high speed data transmission networks rely on optical transceivers and similar devices for facilitating transmission and reception of digital data embodied in the form of optical signals over optical fibers. Optical networks are thus found in a wide variety of high speed applications ranging from as modest as a small Local Area Network (LAN) to as grandiose as the backbone of the Internet.
Typically, data transmission in such networks is implemented by way of an optical transmitter (also referred to as an electro-optic transducer), such as a laser or Light Emitting Diode (LED). The electro-optic transducer emits light when current is passed through it, the intensity of the emitted light being a function of the current magnitude being passed through the electro-optic transducer. Information is conveyed optically by transmitting different optical intensities. The emitted light is more specifically emitted by the PN junction of the electro-optic transducer.
The optical emission frequencies from the PN junction of the electro-optic transducer have strong temperature dependencies that can seriously affect performance, depending on the application. For example, in Dense Wavelength Division Multiplexed (DWDM) laser applications, different optical channels are transmitted simultaneously, each optical channel having a tight frequency range that the corresponding optical signal should stay within. Any variance outside of the frequency range could cause inter-signal interference, seriously increasing the error rate of the transmission. Thus, in DWDM laser applications, it is critical that the laser's transmitted frequency be tightly controlled. Nevertheless, the frequency characteristics of the emitted light from the PN laser diode junction are heavily temperature-dependent. Although DWDM has been discussed here, there are a wide variety of applications in which it may be desirable to accurately control the temperature of the electro-optic transducer junction.
The temperature control of the electro-optic transducer junction typically relies on a temperature feedback system. Specifically, a temperature sensor is provided in proximity to the electro-optic transducer junction. Depending on the sensed temperature, a temperature driver then heats or cools the temperature sensor as appropriate until the temperature sensor detects a temperature within an acceptable temperature range. The aim here is that by tightly controlling the temperature of the temperature sensor, the temperature of the proximate electro-optic transducer driver junction will also be tightly controlled.
However, the temperature sensor and the electro-optic transducer junction cannot occupy the same space at the same time. Therefore, the temperature sensor, though relatively close to the electro-optic transducer junction, is still placed some finite distance from the electro-optic transducer junction. There will thus be some finite amount of thermal resistance between the temperature sensor and the electro-optic transducer junction.
The temperature of the electro-optic transducer junction may vary significantly as the electro-optic transducer itself generates heat. Furthermore, the temperature sensor may also generate heat. In addition, the temperature sensor and the electro-optic transducer may dynamically exchange heat with other surrounding components and the environment. Thus, due to the thermal resistance between the temperature sensor and the electro-optic transducer, there will be some error between the temperature sensed by the temperature sensor and the actual temperature of the electro-optic transducer junction. In this way, even very tight control of the temperature of the temperature sensor, will not necessarily result in tight control of the temperature of the electro-optic transducer junction.
Accordingly, what would be advantageous are mechanisms in which there is tighter control of the temperature of the electro-optic transducer junction.